WPF Discussion Boards

3-Feb-11 11:45

You could simply add a dirty flag and bind to this.

I'm not a stalker, I just know things. Oh by the way, you're out of milk.

Forgive your enemies - it messes with their heads

Re: An MVVM way to know when a database update is complete in order to navigate to another page.

_Maxxx_3-Feb-11 14:32

_Maxxx_

3-Feb-11 14:32

Your VM needs to expose some property that indicates success or failure.

You might need a converter because there are three or four states you're talking about:
1. Don't have a pending update
2. Have a pending update
3. Update failed
4. Update passed

(2. is only appropriate for asynchronous updates)

So your VM has a property that starts off with a value 1.
When the 'save' command is triggered, it is set to 2.
When the results of the Save are returned t is set to 3 or 4 respectively.

You could 'merge' this with any process you are using to enable/disable the Save button - so add another state ...

0. Nothing To Save

___________________________________________
.\\axxx
(That's an 'M')

Re: An MVVM way to know when a database update is complete in order to navigate to another page.

Abhinav S3-Feb-11 21:33

Abhinav S

3-Feb-11 21:33

Bind the status to a textblock and create a property for it in your view model (assuming everything is bound to the view model).

Once your async web service comese back from the server, fire an action to get to the view model and then let INotifyPropertyChanged take over to update the status.

The funniest thing about this particular signature is that by the time you realise it doesn't say anything it's too late to stop reading it.

My latest tip/trick

Re: An MVVM way to know when a database update is complete in order to navigate to another page.

ToddHileHoffer4-Feb-11 2:33

ToddHileHoffer

4-Feb-11 2:33

This is what I did. I guess the user will have to click a link to navigate, or I can put that in the code behind. Thanks for the reply.

I didn't get any requirements for the signature

Re: An MVVM way to know when a database update is complete in order to navigate to another page.

Abhinav S7-Feb-11 19:14

Abhinav S

7-Feb-11 19:14

Strange. You should not need to - are the datacontext's correct?

The funniest thing about this particular signature is that by the time you realise it doesn't say anything it's too late to stop reading it.

My latest tip/trick

Re: An MVVM way to know when a database update is complete in order to navigate to another page.

Mycroft Holmes7-Feb-11 19:28

Mycroft Holmes

7-Feb-11 19:28

We use the MVVMlight framework from Galasoft, it has a messaging construct. In the completed method we send the name of the method via a Completed message pump, the relevant view or viewmodel subscribes to the Completed message, checks the message content and takes action as appropriate.

We use a VERY simplified structure, I know it can get a lot more complex but this meets our current needs.

However I rarely (never) use it to navigate as the datacontext generally meets our needs (data refreshes after the call and updates the UI via onpropertychanged)

Never underestimate the power of human stupidity
RAH

Add Controls Dynamically Using MVVM

Kevin Marois3-Feb-11 8:20

Kevin Marois

3-Feb-11 8:20

I'm working on a WPF app that has to have rows of controls added at runtime. The rows will be fairly simple - Caption and TextBox, and in some cases, a button to the right.

Since I'm using MVVM, all the View has is:

<ScrollViewer VerticalScrollBarVisibility="Auto">
    <StackPanel Name="pnlControls"/>
</ScrollViewer>

Now in the ViewModel when I pull the data that represents the rows, how do I add them to pnlControls?

Thaks

Everything makes sense in someone's mind

dasblinkenlight3-Feb-11 8:50

dasblinkenlight

3-Feb-11 8:50

In the code where you read your rows, add something like this:

    // ...
    foreach (var row in myRows) {
        var btn = new Button {Content=row.ButtonCaption};
        btn.Click += NotifyButtonCallback;
        pnlControls.Children.Add(btn);
        var txt = new TextBox {Text=row.TextBoxText};
        pnlControls.Children.Add(txt);
    }
    // ...

private void NotifyButtonCallback(object sender, RoutedEventArgs e) {
    //...
}

You will need some additional "bookkeeping" to establish a connection between a UI element that you create dynamically and the row from which you created it, so that you could act upon user's actions, such as editing the text or clicking a button.

Kevin Marois3-Feb-11 9:04

Kevin Marois

3-Feb-11 9:04

But the problem is that pnlControls is not accessable from within the ViewModel.

Everything makes sense in someone's mind

RobCroll3-Feb-11 13:37

RobCroll

3-Feb-11 13:37

You should really handle this in the View not the ModelView. The ModelView should be independent of the View. MVVM light has a nice messenger pattern which you can use. Basically when the ModelView determines a new control needs to be added, it transmits a message which the View subscribes to. The View receives the message and then adds the control.

I'm not a huge fan of MVVM so others may argue the point but that's how I do it.

"You get that on the big jobs."

_Maxxx_3-Feb-11 15:31

_Maxxx_

3-Feb-11 15:31

You need to bind to a collection in your viewmodel and use a DataTemplate to describe how the buttons are to be displayed.

If it wasn't for the fact that I'm in the middle of debugging MS Access programs, I'd probably be able to find an example!!

___________________________________________
.\\axxx
(That's an 'M')

Help editing Xml file from code - C#

_Maxxx_3-Feb-11 15:54

_Maxxx_

3-Feb-11 15:54

Got bored with the MS Access - here's a real simple example...

The temnplate tells it how to display. THe vm has an Options property containing a collection of Option - each of which has an OptionName property

<base:BaseView.Resources>
    <DataTemplate x:Key="ButtonTemplate">
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="100" />
            </Grid.ColumnDefinitions>
            <Button  Content="{Binding OptionName}" Height="32"/>
        </Grid>
    </DataTemplate>

</base:BaseView.Resources>

<StackPanel Background="#FFFF00" Height="150">
	<ItemsControl  ItemsSource="{Binding Options}"
			ItemTemplate="{StaticResource ButtonTemplate}">
			<ItemsControl.ItemsPanel>
				<ItemsPanelTemplate>
					<StackPanel Orientation="Vertical" HorizontalAlignment="Center" />
				</ItemsPanelTemplate>
			</ItemsControl.ItemsPanel>
	</ItemsControl>
</StackPanel>

Hope that's enough to get you started - you need to work out how you're going to handle clicks, of course... each button may bind to the same command with a varying parameter, or each to its own command - I haven't done this bit (back to the MS Access now!)

___________________________________________
.\\axxx
(That's an 'M')

jadughar3-Feb-11 5:46

jadughar

3-Feb-11 5:46

Hi
I'm trying to modify an Xml file. This is the content of the Xml. The problem is that after changes, it will creates a copy of the content of the Xml file without changing the old content.

Before changes :

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="Application.Properties.Settings.DBConnectionString"
      connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\DB.mdb"
      providerName="System.Data.OleDb" />
  </connectionStrings>
</configuration>

After changes :

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="Application.Properties.Settings.DBConnectionString"
      connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\DB.mdb"
      providerName="System.Data.OleDb" />
  </connectionStrings>
</configuration>
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="Application.Properties.Settings.DBConnectionString"
      connectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\DataBase\DB.mdb"
      providerName="System.Data.OleDb" />
  </connectionStrings>
</configuration>

The code is :

//xml document object
System.Xml.XmlDocument xdoc = new System.Xml.XmlDocument();

FileStream reader = new FileStream(this._XmlFilePath, FileMode.Open, FileAccess.ReadWrite);

xdoc.XmlResolver = null;

//load the xml file
xdoc.Load(reader);

System.Xml.XmlElement Node = (System.Xml.XmlElement)xdoc.DocumentElement.SelectSingleNode("//configuration/connectionStrings/add[@name=\"Application.Properties.Settings.DBConnectionString\"]");
if (Node != null)
{
    //key found, set the value
    Node.Attributes.GetNamedItem("Source").Value = "C:\DataDabe\DB.mdb";

    //finally, save the new version of the config file
    xdoc.Save(reader);
    reader.Close();
}

"For as long as men massacre animals, they will kill each other. Indeed, he who sows the seed of murder and pain cannot reap joy and love." Pythagoras

Pete O'Hanlon3-Feb-11 8:03

3-Feb-11 8:03

Nope. I don't see what this has to do with WPF or Silverlight. Wrong forum I'm afraid.

I'm not a stalker, I just know things. Oh by the way, you're out of milk.

Forgive your enemies - it messes with their heads

RobCroll3-Feb-11 13:54

RobCroll

3-Feb-11 13:54

Check out the ConfigurationManager class. It looks like you are trying to edit the app.config file and this would be a better approach.

"You get that on the big jobs."

Abhinav S3-Feb-11 20:30

Abhinav S

3-Feb-11 20:30

You've got the wrong forum unfortunately.
This is the XAML forum and not the XML forum.
Wink | ;)

The funniest thing about this particular signature is that by the time you realise it doesn't say anything it's too late to stop reading it.

My latest tip/trick

jadughar3-Feb-11 21:26

jadughar

3-Feb-11 21:26

Oh sorry..this was an Window form application...wrong forum

sorry again
bye

"For as long as men massacre animals, they will kill each other. Indeed, he who sows the seed of murder and pain cannot reap joy and love." Pythagoras

wpf

arkiboys2-Feb-11 11:54

2-Feb-11 11:54

I have populated a combo box as follows:

<ComboBox Height="23" HorizontalAlignment="Left" Margin="120,6,0,0"
Name="cboHealth" SelectedIndex="{Binding Path=HealthLevelID}"
VerticalAlignment="Top" Width="256" />

private void PopulateHealthLevels()
{
List<clsDetails> healthlevels = new List<clsDetails>();
healthlevels = clsAccess.GetHealthLevels();
foreach (clsDetails details in healthlevels)
{
cboHealth.Items.Add(details.HealthLevelName);
}
}

The datatable returns the HealthLevelID field as well as otherr fields.
HealthLevelID has values of 1 and 2 for Normal and unNormal respectively.
The combo box does get populated but it does not show the correct item for the selected row.
What am I doing wrong please?
Thanks

Re: wpf

Pete O'Hanlon3-Feb-11 0:04

3-Feb-11 0:04

A couple of things here.

1. Your title needs some work. Simply stating wpf is not enough.
2. The code should be enclosed in pre tags.

Now, your problem lies in the fact that SelectedIndex is actually zero based, so your values will not match. SelectedIndex should only be used to indicate the relative position of the object in your collection.

I'm not a stalker, I just know things. Oh by the way, you're out of milk.

Forgive your enemies - it messes with their heads

Re: wpf

arkiboys3-Feb-11 0:17

wpf, populate combobox accordingly

3-Feb-11 0:17

Hi,
At present the HealthLevelID has only values 1 or 2 in it's tblHealthlevels table.
Do you mean that since I am using selectedindex in xamml, I can change the integer values in the sql server table to be 0 and 1 instead of 1 and 2 and then it will work? If so, what if I add more values in the table such as 1, 2, 3, 4, ...
Will my existing xaml work ok?
Thanks

arkiboys3-Feb-11 10:48

Re: wpf, populate combobox accordingly

3-Feb-11 10:48

I did do what you mentioned but still unable to solve this issue.
Any thoughts please?

Pete O'Hanlon3-Feb-11 11:47

3-Feb-11 11:47

Rather than relying on the selected index, I prefer to use a selected item.

I'm not a stalker, I just know things. Oh by the way, you're out of milk.

Forgive your enemies - it messes with their heads

Re: wpf, populate combobox accordingly

arkiboys3-Feb-11 11:52